Head-mounted display

ABSTRACT

Methods and apparatus provide for: disposing a display unit in front of eyes of a user; disposing an optical system between the display unit and the eyes of the user; and disposing an imaging unit between the display unit and the optical system, the imaging unit imaging the display unit in which an image of the eyes of the user is reflected; and irradiating light onto the eyes of the user, where the imaging includes imaging the eyes of the user reflected in the display unit by reflecting the light irradiated by the light-irradiation unit by the eyes of the user.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.15/747,269, accorded a filing date of Jan. 24, 2018, which is a nationalstage application of International Application No. PCT/JP2016/072967,filed Aug. 4, 2016, which claims priority to JP Application No.2015-158976, filed Aug. 11, 2015, the entire disclosures of which arehereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a head-mounted display.

BACKGROUND ART

In a head-mounted display or the like that is worn on a head of a userand in which a video or the like is viewed as disclosed in PTL 1 to 4, atechnique has been known in which a position of eyes or line-of-sightdirection of the user is detected from an image of the eyes of the userphotographed by a camera.

Citation List Patent Literature

[PTL 1] JP 2015-508182T; [PTL 2] JP 2002-301030A; [PTL 3] JP1997-127459A; [PTL 4] JP 2012-515579T

SUMMARY Technical Problem

When photographing eyes of a user that wears a head-mounted display, acamera is installed in a location (for example, an upper portion orlower portion of an optical system) that is a space between the eyes ofthe user and the optical system disposed between a display unit and theeyes of the user, and that has no obstruction in viewing the displayunit by the user.

Herein, in the head-mounted display that is worn on a head, a distancebetween the optical system and the eyes of the user that wears thehead-mounted display becomes small. Also, an actual state is that a sizeof the optical system is preferably larger in order to broaden a fieldof view of the user. Then, there occurs a problem that a photographingangle of the camera to the eyes of the user becomes shallow and it isdifficult to photograph the eyes of the user with eyelids, eyelashes, orthe like becoming an obstacle.

In view of the foregoing, it is an object of the present invention toprovide the head-mounted display in which it is easy to photograph theeyes of the user that wears the head-mounted display.

Solution to Problem

In order to solve the above-described problem, a head-mounted displayworn by a user according to the present invention, includes a displayunit disposed in front of eyes of the user, an optical system disposedbetween the display unit and the eyes of the user, and an imaging unitdisposed between the display unit and the optical system, the imagingunit imaging the display unit in which an image of the eyes of the useris reflected.

In a mode of the present invention, it may be assumed that thehead-mounted display further includes a light-irradiation unit thatirradiates light onto the eyes of the user, and the imaging unit imagesan image of the eyes of the user reflected in the display unit byreflecting the light irradiated by the light-irradiation unit by theeyes of the user.

In this mode, it may be assumed that the light-irradiation unit isdisposed between the optical system and the eyes of the user anddirectly irradiates light onto the eyes of the user.

Further, it may be assumed that the light-irradiation unit is disposedbetween the display unit and the optical system and irradiates, onto theeyes of the user, reflected light in which light irradiated onto thedisplay unit is reflected.

Further, it may be assumed that the light-irradiation unit irradiatesinfrared light, and the imaging unit is an infrared camera capable ofimaging the infrared light.

Further, in a mode of the present invention, it may be assumed that thehead-mounted display further includes a line-of-sight detection unitthat detects a line-of-sight direction of the user on the basis of animage including the image of the eyes of the user imaged by the imagingunit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an example of a hardware configurationof a head-mounted display (HMD) according to an embodiment of thepresent invention.

FIG. 2 is a schematic diagram illustrating a first example of aconfiguration of the HMD according to the present embodiment.

FIG. 3 is a schematic diagram illustrating a configuration of the HMDaccording to a contrast example.

FIG. 4 is a schematic diagram illustrating a second example of aconfiguration of the HMD according to the present embodiment.

FIG. 5 is a schematic diagram illustrating a first modification exampleof a configuration of the HMD according to the present embodiment.

FIG. 6 is a schematic diagram illustrating a second modification exampleof a configuration of the HMD according to the present embodiment.

DESCRIPTION OF EMBODIMENT

Hereinafter, an embodiment of the present invention will be describedwith reference to the accompanying drawings.

FIG. 1 is a diagram illustrating an example of a hardware configurationof an HMD 10 according to an embodiment of the present invention. FIG. 2is a schematic diagram illustrating a first example of a configurationof the HMD 10 according to the present embodiment.

As illustrated in FIG. 1, the HMD 10 according to the present embodimentincludes, for example, a control unit 11, a storage unit 12, aninput/output unit 13, a display unit 14, a light-irradiation unit 15,and an imaging unit 16.

The control unit 11 includes a program control device such as a centralprocessing unit (CPU), and executes various types of informationprocessing in accordance with programs stored in the storage unit 12.

The storage unit 12 includes a memory device such as a random accessmemory (RAM) or read-only memory (ROM), and stores programs or the likeexecuted by the control unit 11. Further, the storage unit 12 alsofunctions as a work memory of the control unit 11.

The input/output unit 13 is an input/output interface such as ahigh-definition multimedia interface (HDMI) (registered trademark) portor a universal serial bus (USB) port, for example.

The display unit 14 is a display such as a liquid crystal display or anorganic electroluminescence (EL) display, for example. The display unit14 according to the present embodiment displays, for example, a video orthe like expressed by video signals received from an entertainmentapparatus such as a home game machine, digital versatile disc (DVD)player, or Blue-ray (registered trademark) player connected via theinput/output unit 13. In addition, the display unit 14 according to thepresent embodiment may be capable of displaying a three-dimensionalvideo.

The light-irradiation unit 15 is an optical device such as alight-emitting diode (LED). The light-irradiation unit 15 according tothe present embodiment is assumed to irradiate light of a wavelengthband other than a visible light band, called infrared light; however,the light-irradiation unit 15 is not limited to this example, and may beassumed to irradiate light of the visible light band.

The imaging unit 16 is a camera such as a digital camera for generatingan image in which an object is imaged, for example. The imaging unit 16according to the present embodiment is assumed to be an infrared cameracapable of imaging infrared light; however, the imaging unit 16 is notlimited to this example, and may be a camera capable of imaging visiblelight. Further, as illustrated in FIG. 2, the imaging unit 16 accordingto the present embodiment is disposed so as to image the display unit 14and images the display unit 14 in which an image 40 of eyes of a userobtained by using infrared light reflected by eyes 30 of the user isreflected. In addition, the imaging unit 16 may be assumed to image thedisplay unit 14 in which the image 40 of the eyes of the user obtainedby using visible light reflected by the eyes 30 of the user isreflected.

The control unit 11 further detects a position of the eyes of the useror a line-of-sight direction of the user from an image including theimage 40 of the eyes of the user imaged by the imaging unit 16. Thecontrol unit 11 is assumed to detect the position of the eyes of theuser or the line-of-sight direction by using a known line-of-sightdetection technique. For example, the control unit 11 detects theposition of the eyes of the user or the line-of-sight direction of theuser on the basis of a positional relationship between pupils of theuser and a basic point obtained by reflecting infrared light by corneasof the user. Alternatively, on the basis of the position of irises orpupils, the control unit 11 may detect the position of the eyes of theuser or the line-of-sight direction of the user. In addition, theimaging unit 16 may include a function of detecting the position of theeyes of the user or the line-of-sight direction of the user.

As described above, the position of the eyes of the user or theline-of-sight direction of the user detected from an image including theimage 40 of the eyes of the user imaged by the imaging unit 16 isapplicable to calibration of the HMD 10 or a line-of-sight trackingfunction of the user. The calibration of the HMD 10 is for adjusting adisplay position of a video in the display unit 14 at the time ofstarting up the HIVID 10, at the time of starting up applications, orthe like; for example, the display position of the video can be adjustedso that the video is displayed in the position of the eyes of the useron the display unit 14 by using the detected position of the eyes of theuser. In the line-of-sight tracking function of the HMD 10, for example,a line-of-sight tracking can be performed by using the detectedline-of-sight direction of the user.

In addition, the image including the image 40 of the eyes of the userimaged by the imaging unit 16 may be assumed to be transmitted to anexternal information processing apparatus via the input/output unit 13.In this case, the position of the eyes of the user or the line-of-sightdirection of the user is assumed to be detected by using the imageincluding the image 40 of the eyes of the user received by the externalinformation processing apparatus.

In the first example of the configuration of the HMD 10 according to thepresent embodiment illustrated in FIG. 2, a state in which the userwears the HMD 10 is illustrated. As illustrated in FIG. 2, in the HMD 10according to the present embodiment, the display unit 14 and an opticalsystem 17 including at least one optical member such as a mirror, alens, or a prism are disposed in front of the eyes of the user. That is,the optical system 17 is disposed in front of the eyes of the user andthe display unit 14 is disposed at a front surface of the eyes 30 of theuser through the optical system 17. Further, it is assumed that when adistance from the display unit 14 to the optical system 17 is X and adistance from the optical system 17 to the eyes 30 of the user is Y, thedistance Y is shorter than the distance X. In particular, in the HMD 10worn by the user, the distance Y tends to become short. In theabove-described HMD 10 according to the present embodiment, video lightoutput from the display unit 14 passes through the optical system 17 andis made incident on the eyes 30 of the user, and thereby the user canview a video displayed on the display unit 14. Further, thelight-irradiation unit 15 is disposed between the optical system 17 andthe eyes 30 of the user and irradiates infrared light onto the eyes 30of the user. The imaging unit 16 is a camera capable of imaging infraredlight and is disposed facing to the display unit 14 between the displayunit 14 and the optical system 17. Herein, it is assumed that a verticaldistance between the imaging unit 16 and a straight line incidentvertically on the display unit 14 from the eyes 30 of the user is H1 anda vertical distance between the display unit 14 and the imaging unit 16is L1.

In the HMD 10 according to the present embodiment illustrated in FIG. 2,the infrared light irradiated onto the eyes 30 of the user by thelight-irradiation unit 15 is reflected by the eyes 30 of the user;further, the reflected light passes through the optical system 17 and ismade incident on the display unit 14, and thereby the image 40 of theeyes of the user by the infrared light is reflected in the display unit14. Then, the imaging unit 16 images the display unit 14 in which theimage 40 of the eyes of the user by the infrared light is reflected. Inaddition, the image 40 of the eyes of the user by the infrared light maybe only required to indicate the pupils of the user and the basic pointobtained by reflecting the infrared light by the corneas of the user;further, the imaging unit 16 may be disposed so as to image a portion ofthe display unit 14 in which the above-described image 40 of the eyes ofthe user is reflected. As described above, in the HMD 10 according tothe present embodiment illustrated in FIG. 2, a photographing angle ofthe imaging unit 16 to the image 40 of the eyes of the user reflected inthe display unit 14 is θ₁. It is to be noted that, in FIG. 2, thephotographing angle θ₁ to a center of the image 40 of the eyes of theuser reflected in the display unit 14 is illustrated as an example.

Subsequently, a contrast example with the HMD 10 according to thepresent embodiment illustrated in FIG. 2 will be described. FIG. 3 is aschematic diagram illustrating a configuration of an HMD 110 accordingto the contrast example. In the HMD 110 according to the contrastexample illustrated in FIG. 3, a display unit 114 and an optical system117 including at least one optical member such as a mirror, a lens, or aprism are disposed in front of the eyes of the user. That is, theoptical system 117 is disposed in front of the eyes of the user and thedisplay unit 114 is disposed at the front surface of eyes 130 of theuser through the optical system 117. Further, a light-irradiation unit115 is disposed between the optical system 117 and the eyes 130 of theuser and irradiates infrared light onto the eyes 130 of the user. Animaging unit 116 is a camera capable of imaging infrared light and isdisposed facing to the eyes 130 of the user between the optical system117 and the eyes 130 of the user. In addition, the display unit 114, thelight-irradiation unit 115, the imaging unit 116, and the optical system117 of the HMD 110 according to the contrast example illustrated in FIG.3 are assumed to be the same as the display unit 14, thelight-irradiation unit 15, the imaging unit 16, and the optical system17 of the HMD 10 according to the present embodiment illustrated in FIG.2, respectively. Thus, a distance X from the display unit 114 to theoptical system 117 and a distance Y from the optical system 117 to theeyes 130 of the user are assumed to be the same as those of the HMD 10according to the present embodiment illustrated in FIG. 2.

In the HMD 110 according to the contrast example illustrated in FIG. 3,the infrared light irradiated onto the eyes 130 of the user by thelight-irradiation unit 115 is reflected by the eyes 130 of the user andthe reflected light is made incident on the imaging unit 116. Asdescribed above, the imaging unit 116 of the HMD 110 according to thecontrast example is capable of imaging the pupils of the user and thebasic point obtained by reflecting the infrared light irradiated by thelight-irradiation unit 115 by the corneas of the user. Further, in theHMD 110 according to the contrast example illustrated in FIG. 3, aphotographing angle of the imaging unit 116 to the eyes 130 of the useris θ₂. It is to be noted that, in FIG. 3, the photographing angle θ₂ toa center of the eyes 130 of the user is illustrated as an example.

Herein, the HMD 10 according to the present embodiment illustrated inFIG. 2 and the HMD 110 according to the contrast example illustrated inFIG. 3 are compared with each other.

First, in the HMD 10 according to the present embodiment, the imagingunit 16 is preferably disposed in a location in which it is easy toimage the image 40 of the eyes of the user reflected in the display unit14 and a video displayed on the display unit 14 by the user is notprevented from being viewed. In the HMD 10 according to the presentembodiment as illustrated in FIG. 2, for example, the imaging unit 16 isdisposed at the end of the optical system 17 that is a position near tothe optical system 17. That is, the vertical distance L1 between thedisplay unit 14 and imaging unit 16 in the HMD 10 according to thepresent embodiment is a value approximate to the distance X. Further,the vertical distance H1 between the imaging unit 16 and a straight lineincident on the display unit 14 vertically from the eyes 30 of the useris a value according to a size of the optical system 17 and the positionof the eyes of the user and is, for example, approximately half of aheight of the optical system 17.

Subsequently, in the HMD 110 according to the contrast example, theimaging unit 116 is preferably disposed in a location in which it iseasy to image the eyes 130 of the user and a video displayed on thedisplay unit 114 is not prevented from being viewed by the user. In theHMD 110 according to the contrast example as illustrated in FIG. 3, forexample, the imaging unit 116 is disposed at the end of the opticalsystem 117 that is a position near to the optical system 117. That is, avertical distance L2 between the eyes 30 of the user and the imagingunit 116 in the HMD 110 according to the contrast example is a valueapproximate to the distance Y. Further, a vertical distance H2 betweenthe imaging unit 116 and a straight line incident on the display unit114 vertically from the eyes 130 of the user is a value according to asize of the optical system 117 and the position of the eyes of the userand is, for example, approximately half of a height of the opticalsystem 117. It is to be noted that, in the HMD 110 according to thecontrast example illustrated in FIG. 3, as the distance Y is shorter andas the size of the optical system 117 is larger, the photographing angleθ₂ of the imaging unit 116 to the eyes 130 of the user is shallower andeyelashes, eyelids, or the like of the user become an obstacle to theimaging.

As described above, in FIGS. 2 and 3, the vertical distance H1 in theHMD 10 according to the present embodiment is approximately the same asthe vertical distance H2 in the HMD 110 according to the contrastexample. Further, the vertical distance L1 in the HMD 10 according tothe present embodiment is longer than the vertical distance L2 in theHMD 110 according to the contrast example. Therefore, the photographingangle 74 ₁ of the imaging unit 16 to the image 40 of the eyes of theuser reflected in the display unit 14 according to the presentembodiment is larger than the photographing angle θ₂ of the imaging unit116 to the eyes 130 of the user according to the contrast example. Asdescribed above, the imaging unit 16 according to the present embodimentimages the display unit 14 in which the image 40 of the eyes of the useris reflected, and thereby it is possible to deepen the photographingangle of the imaging unit 16 to the image 40 of the eyes of the user andit is easy to photograph the image 40 of the eyes of the user.

In the above-described example, an example is provided in which thevertical distance H1 in the HMD 10 according to the present embodimentis approximately the same as the vertical distance H2 in the HMD 110according to the contrast example, and the vertical distance L1 in theHMD 10 according to the present embodiment is longer than the verticaldistance L2 in the HMD 110 according to the contrast example; however,the present embodiment is not limited to this example. For example, thevertical distance H1 in the HMD 10 according to the present embodimentmay be larger than half of the height of the optical system 17. Further,the vertical distance L1 in the HMD 10 according to the presentembodiment may be shorter than the distance X or may be shorter than thedistance Y. Even in this case, the imaging unit 16 according to thepresent embodiment images the display unit 14 in which the image 40 ofthe eyes of the user is reflected, and thereby there is not present anobstacle to the imaging such as the eyelashes or eyelids of the user asin the HMD 110 according to the contrast example, and therefore it iseasy to image the image 40 of the eyes of the user.

The imaging unit 16 further images the display unit 14 in which theimage 40 of the eyes of the user by the infrared light is reflected, andthereby the image 40 of the eyes of the user can be imaged even duringthe period in which videos or the like received from entertainmentapparatus are displayed on the display unit 14. That is, the infraredlight is irradiated onto the eyes of the user, and thereby the image 40of the eyes of the user can be reflected in the display unit 14 withoutobstructing the video displayed on the display unit 14. Through thisprocessing, even while the user views the video or the like receivedfrom the entertainment apparatus, the control unit 11 is capable ofdetecting the position of the eyes of the user or the line-of-sightdirection of the user and performing the calibration or theline-of-sight tracking. For example, a line-of-sight input operation canbe used as a user input operation to be accepted while the video or thelike received from the entertainment apparatus is displayed on thedisplay unit 14; further, the entertainment apparatus is capable ofperforming processing relating to the input operation according to theposition of the eyes of the user or the line-of-sight direction of theuser.

Further, in the HMD 10 according to the present embodiment illustratedin FIG. 2, the imaging unit 16 may be assumed to be a camera capable ofimaging visible light. In this case, the imaging unit 16 is assumed toperform image processing such as filtering processing to an imageobtained by imaging the display unit 14 and thereby extract the image 40of the eyes of the user by the infrared light.

Further, in the HMD 10 according to the present embodiment illustratedin FIG. 2, it may be assumed that the imaging unit 16 is a cameracapable of imaging visible light and further the light-irradiation unit15 is not disposed. Even when the light-irradiation unit 15 is notdisposed, reflected light obtained by reflecting visible light by theeyes 30 of the user passes through the optical system 17 and is madeincident on the display unit 14, and thereby the image 40 of the eyes ofthe user by the visible light is reflected in the display unit 14. Then,the imaging unit 16 may be assumed to image the display unit 14 in whichthe image 40 of the eyes of the user by the visible light is reflected.Herein, when the imaging unit 16 images the display unit 14 in which theimage 40 of the eyes of the user by the visible light is reflected, theimaging unit 16 preferably images the display unit 14 during the periodin which the video or the like received from the entertainment apparatusis not displayed on the display unit 14.

FIG. 4 is a schematic diagram illustrating a second example of aconfiguration of the HMD 10 according to the present embodiment. The HMD10 according to the present embodiment illustrated in FIG. 4 is obtainedby making different a position of the light-irradiation unit 15 of theHMD 10 according to the present embodiment illustrated in FIG. 2. Thelight-irradiation unit 15 of the HMD 10 according to the presentembodiment illustrated in FIG. 4 is disposed between the display unit 14and the optical system 17 and irradiates the infrared light calledinfrared laser onto the display unit 14. The other configurations aresimilarly to those of the HMD 10 according to the present embodimentillustrated in FIG. 2, and therefore redundant descriptions are omittedherein.

In the HMD 10 according to the present embodiment illustrated in FIG. 4,the infrared light irradiated onto the display unit 14 by thelight-irradiation unit 15 is reflected by the display unit 14; further,the reflected light passes through the optical system 17 and isirradiated onto the eyes 30 of the user. Then, the infrared lightirradiated onto the eyes 30 of the user is reflected by the eyes 30 ofthe user; further, the reflected light passes through the optical system17 again and is made incident on the display unit 14, and thereby theimage 40 of the eyes of the user by the infrared light is reflected inthe display unit 14. Then, the imaging unit 16 images the display unit14 in which the image 40 of the eyes of the user is reflected. Asdescribed above, the reflected light obtained by reflecting the infraredlight irradiated onto the display unit 14 is irradiated onto the eyes 30of the user and thereby the infrared light is made incident on the eyes30 of the user from the front side. Thus, since the image 40 of the eyesof the user is easily reflected in the display unit 14, the imaging unit16 easily images the display unit 14 in which the image 40 of the eyesof the user is reflected. Thus, an accuracy of detection in the positionof the eyes of the user or in the line-of-sight direction of the userthrough the control unit 11 is improved.

In addition, the configuration of the HMD 10 illustrated in FIGS. 2 and4 is consistently one example and is not limited to this example. In theabove-described example, in FIGS. 2 and 4, an example is provided inwhich the light-irradiation unit 15 and the imaging unit 16 are disposedon the upper side of the HIVID 10; further, for example, thelight-irradiation unit 15 and the imaging unit 16 may be disposed on thelower side of the HMD 10 or may be disposed on the side surface side ofthe HMD 10. These dispositions may be appropriately set in accordancewith characteristics of the display unit 14 or the optical system 17,the distance X from the display unit 14 to the optical system 17, thedistance X2 from the optical system 17 to the eyes 30 of the user, orthe like.

Modification Example

FIG. 5 is a schematic diagram illustrating a first modification exampleof the configuration of the HMD 10 according to the present embodiment.FIG. 5 illustrates a state in which the user wears the HMD 10. In theHMD 10 according to the modification example illustrated in FIG. 5, theoptical system 17 is disposed in front of the eyes of the user and theimaging unit 16 is disposed at the front surface of the eyes 30 of theuser through the optical system 17. The optical system 17 includes amirror 27 that reflects visible light and transmits infrared light andis disposed between the imaging unit 16 and the eyes 30 of the user. Thedisplay unit 14 is disposed so that video light output from the displayunit 14 is reflected by the mirror 27 and is made incident on the eyes30 of the user. The light-irradiation unit 15 is disposed between theoptical system 17 and the eyes 30 of the user and irradiates theinfrared light onto the eyes 30 of the user. The imaging unit 16 isassumed to be an infrared camera capable of imaging the infrared light.

In the HMD 10 according to the modification example illustrated in FIG.5, the infrared light irradiated onto the eyes 30 of the user by thelight-irradiation unit 15 is reflected by the eyes 30 of the user, andthe reflected light is transmitted through the mirror 27 and is madeincident on the imaging unit 16. This processing permits the imagingunit 16 to image the eyes 30 of the user to the eyes 30 of the user fromthe front side.

FIG. 6 is a schematic diagram illustrating a second modification exampleof the configuration of the HMD 10 according to the present embodiment.The HMD 10 according to the modification example illustrated in FIG. 6is obtained by making different the position of the light-irradiationunit 15 of the HMD 10 according to the modification example illustratedin FIG. 5. The light-irradiation unit 15 of the HMD 10 according to themodification example illustrated in FIG. 6 is disposed in front of theeyes of the user through the optical system 17. The other configurationsare similarly to those of the HMD 10 according to the modificationexample illustrated in FIG. 5, and therefore redundant descriptions areomitted herein.

In the HMD 10 according to the modification example illustrated in FIG.6, the infrared light irradiated by the light-irradiation unit 15 istransmitted through the mirror 27 and is irradiated onto the eyes 30 ofthe user. Then, the infrared light irradiated onto the eyes 30 of theuser is reflected by the eyes 30 of the user; further, the reflectedlight is transmitted through the mirror 27 and is made incident on theimaging unit 16. This processing permits the light-irradiation unit 15to irradiate the infrared light onto the eyes 30 of the user from thefront side, and permits the imaging unit 16 to image the eyes 30 of theuser to the eyes 30 of the user from the front side.

1. A head-mounted display worn by a user, comprising: a display unitdisposed in front of eyes of the user; an optical system disposedbetween the display unit and the eyes of the user; and an imaging unitdisposed between the display unit and the optical system, the imagingunit imaging the display unit in which an image of the eyes of the useris reflected; a light-irradiation unit that irradiates light onto theeyes of the user, wherein the imaging unit images an image of the eyesof the user reflected in the display unit by reflecting the lightirradiated by the light-irradiation unit by the eyes of the user.
 2. Thehead-mounted display according to claim 1, wherein the light-irradiationunit is disposed between the optical system and the eyes of the user,and irradiates light onto the eyes of the user.
 3. The head-mounteddisplay according to claim 1, wherein the light-irradiation unit isdisposed between the display unit and the optical system and irradiates,onto the eyes of the user, reflected light in which light irradiatedonto the display unit is reflected.
 4. The head-mounted displayaccording to claims 1, wherein: the light-irradiation unit irradiatesinfrared light, and the imaging unit is an infrared camera operable toimage the infrared light.
 5. The head-mounted display according toclaims 1, further comprising: a line-of-sight detection unit thatdetects a line-of-sight direction of the user on a basis of an imageincluding the image of the eyes of the user imaged by the imaging unit.6. The head-mounted display according to claims 1, wherein an incidentangle of light from at least one of the eyes of the user to the displayunit, and a reflection angle of light from the display unit to theimaging unit are different.
 7. A method, comprising: disposing a displayunit in front of eyes of a user; disposing an optical system between thedisplay unit and the eyes of the user; and disposing an imaging unitbetween the display unit and the optical system, the imaging unitimaging the display unit in which an image of the eyes of the user isreflected; and irradiating light onto the eyes of the user, wherein theimaging includes imaging the eyes of the user reflected in the displayunit by reflecting the light irradiated by the light-irradiation unit bythe eyes of the user.